# Math Help - Drawing a graph of function F(x,y)

1. ## Drawing a graph of function F(x,y)

$Z=4x^2+9y^2$
$y^2=-\frac{4}{9}x^2$

How to draw a graph ?
Sqare root turns out to be negative.

2. Originally Posted by totalnewbie
$Z=4x^2+9y^2$
This one is a parabolid which opens up on the z-axis.

$y^2=-\frac{4}{9}x^2$
The problem is like you said.
If x>0 or x<0 then we have a problem because the RHS is negative. Thus, x=0, in that case y=0 too. But there is no restriction on z, thus we move along the z-axis, thus we have a line, in fact, the z-axis.